Ability to filter some relations roles to rebuild the geometry

[flacombe]

Currently, relations geometry rebuild involves all members without filtering. This could lead to unsuitable geometries for length or surface evaluation, as intended by Podoma. Example with https://www.openstreetmap.org/relation/19536760 :

Such an error leads significant length variation. Measured: 12266 m vs Expected: 9798 m

It could be useful to define a list of possible roles to be involved in the geometry rebuild.

Such a filter could be processed when selecting members prior to get the final geometry.